/**
 * Copyright 2011-2014 the original author or authors.
 */
package com.jetdrone.vertx.yoke.middleware;

import javax.crypto.Mac;

import org.jetbrains.annotations.NotNull;
import org.vertx.java.core.Handler;

import com.jetdrone.vertx.yoke.Middleware;
import com.jetdrone.vertx.yoke.core.YokeCookie;
import com.jetdrone.vertx.yoke.store.json.SessionObject;

/**
 * # Session
 */
public class Session extends Middleware {

    private final Mac hmacSHA256;

    private final String name;
    private final String path;
    private final Boolean httpOnly;
    private final long maxAge;

    public Session(@NotNull final String name, @NotNull final String path, final boolean httpOnly, final long maxAge, @NotNull final Mac mac) {
        this.name = name;
        this.path = path;
        this.httpOnly = httpOnly;
        this.maxAge = maxAge;
        hmacSHA256 = mac;
    }

    public Session(@NotNull final String path, final boolean httpOnly, final long maxAge, @NotNull final Mac mac) {
        this("yoke.sess", path, httpOnly, maxAge, mac);
    }

    public Session(final boolean httpOnly, final long maxAge, @NotNull final Mac mac) {
        this("yoke.sess", "/", httpOnly, maxAge, mac);
    }

    public Session(final long maxAge, @NotNull final Mac mac) {
        this("yoke.sess", "/", true, maxAge, mac);
    }

    public Session(@NotNull final Mac mac) {
        this("yoke.sess", "/", true, 60 * 60 * 1000, mac);
    }

    @Override
    public void handle(@NotNull final YokeRequest request, @NotNull final Handler<Object> next) {
        // default session
        final YokeCookie cookie = new YokeCookie(name, hmacSHA256);
        cookie.setPath(path);
        cookie.setHttpOnly(httpOnly);
        cookie.setMaxAge(maxAge);

        // path validation mismatch
        if (request.normalizedPath().indexOf(cookie.getPath()) != 0) {
            next.handle(null);
            return;
        }

        // find the session cookie
        final YokeCookie sessionCookie = request.getCookie(name);
        final YokeResponse response = request.response();

        int hash = 0;
        String unsigned = null;

        if (sessionCookie != null) {
            // session cookies must be signed
            if (sessionCookie.isSigned()) {
                unsigned = sessionCookie.getUnsignedValue();
                if (unsigned != null) {
                    hash = crc16(unsigned);
                }
            }
        }

        final int originalHash = hash;

        // call us when headers are being set for the response
        response.headersHandler(new Handler<Void>() {
            @Override
            public void handle(Void done) {
            	SessionObject session = request.get("session");
                String sessionId = session == null ? null : session.getString("id");

                // removed
                if (sessionId == null) {
                    if (sessionCookie != null) {
                        cookie.setValue("");
                        cookie.setMaxAge(0);
                        response.addCookie(cookie);
                    }
                } else {
                    // only send secure cookies over https
                    if (cookie.isSecure() && !request.isSecure()) {
                        return;
                    }

                    // compare hashes, no need to set-cookie if unchanged
                    if (originalHash != crc16(sessionId)) {
                        // modified session
                        cookie.setValue(sessionId);
                        cookie.sign();
                        response.addCookie(cookie);
                    }
                }
            }
        });

        if (unsigned == null) {
            next.handle(null);
            return;
        }

        request.loadSession(unsigned, next);
    }

    private static final int[] CRC16_TABLE = {
            0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
            0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
            0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
            0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
            0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
            0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
            0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
            0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
            0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
            0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
            0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
            0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
            0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
            0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
            0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
            0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
            0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
            0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
            0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
            0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
            0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
            0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
            0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
            0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
            0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
            0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
            0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
            0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
            0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
            0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
            0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
            0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040,
    };

    private int crc16(String data) {
        byte[] bytes = data.getBytes();
        int crc = 0x0000;
        for (byte b : bytes) {
            crc = (crc >>> 8) ^ CRC16_TABLE[(crc ^ b) & 0xff];
        }

        return crc;
    }
}
